How to Execute Bulk Updates of Primary SMTP Address for Distribution Lists

Like any mail-enabled object managed by Exchange Online, distribution list proxy addresses determine if Exchange can deliver messages to an object. Sometimes the proxy addresses aren’t correct or need adjustment, such as in the case when an organization wants to make sure that all distribution lists have primary SMTP addresses from a specific domain. This article explains how to use PowerShell to adjust the primary SMTP address when necessary.

Why Exchange Online Mailboxes have SharePoint Online Proxy Addresses

A post by the Exchange development group tried to explain why mailboxes have SharePoint Online proxy addresses. It’s all down to the Microsoft 365 substrate, which needs the proxy addresses to ingest digital twins from SharePoint Online into Exchange Online for use by shared services like Microsoft Search. The upshot is that you can’t remove a mailbox permanently without some background processes kicking in to make sure that SharePoint is taken care of.